Radiation protection overview: international aspects
and perspective

I. What is radiation protection?

Radiation protection is a term applied
to concepts, requirements, technologies and operations related to protection
of people (radiation workers, members of the public, and patients undergoing
radiation diagnosis and therapy) against the harmful effects of ionising
radiation. It has its origins early in the twentieth century. The benefits
of radiation were first recognised in the use of X-rays for medical diagnosis,
very soon after the discoveries of radiation and radioactivity. The rush
to exploit the medical benefits led fairly soon to the recognition of
the other side of the coin, that of radiation-induced harm. In those early
days, only the most obvious forms of harm resulting from high doses of
radiation, such as radiation burns , were observed and protection efforts
focused on their prevention, mainly for practitioners rather than patients.
Although the issue was narrow, this was the origin of radiation protection
as a discipline. Over the middle decades of this century, it was gradually
recognised that there were other, less obvious, harmful radiation effects
such as radiation-induced cancer, for which there is a certain risk even
at low doses of radiation. This risk cannot be completely prevented. It
can only be minimised. Therefore, the overt balancing of benefits from
nuclear and radiation practices against radiation risk, and efforts to
reduce the residual risk, have become a major feature of radiation protection.

II. What are the sources of radiation?

Ionising radiation and radioactive
substances are natural and permanent features of the environment. These
sources, called natural background radiation, consist principally of cosmic
rays entering the earth s atmosphere; terrestrial gamma rays due largely
to uranium and thorium, including their decay products, found in various
low concentrations throughout the earth s crust; potassium 40, a radioisotope
which is mixed in small concentrations in nature with stable potassium;
and radon decay products. Through natural background radiation, people
are exposed to external radiation and internal radiation by inhalation
and ingestion of radioactive substances existing in the natural environment.

Artificial radioactivity resulting
from nuclear weapons programmes, principally atmospheric testing, is also
spread throughout the world and exposes people to external radiation and
internal radiation through inhalation and ingestion. However, the average
dose to individuals in the world population from military activities is
very small compared to that resulting from natural background radiation,
and is declining due mainly to the atmospheric test ban treaty of 1963,
but also to the general reduction of nuclear weapons programmes. Some
countries are now faced with the difficult task of decontamination and
stabilisation of military weapons test and production sites.

Additionally, the use of man-made radiation
is widespread. These sources of ionising radiation are called practices.
The use of nuclear energy and applications of its by-products (i.e., ionising
radiation and radioactive substances) continue to increase around the
world. In addition to nuclear power production, nuclear techniques are
used in industry, agriculture, medicine and many fields of research, benefiting
hundreds of millions of people and giving employment to millions of people
in the related occupations. For example, medical X-rays and nuclear medicine
are vital diagnostic tools, and radiotherapy is commonly part of the treatment
of cancer. Large irradiators are used in many countries to sterilise medical
products, preserve foodstuffs and reduce wastage, and sterilisation techniques
have been used to eradicate disease-carrying insects and pests. Industrial
radiography is in routine use to examine welds for defects and help prevent
the failure of engineered structures. Radiotracers are used in many fields
of research.

Figures 1 and 2 show the estimated
percentage dose contribution of various sources, both natural and artificial,
averaged to individual members of the population in the United Kingdom
and the United States, respectively. The percentage contribution of the
sources to any specific individual will vary from the average depending
on a variety of factors (e.g., increased cosmic radiation for those living
at high altitudes, individuals receiving medical radiation diagnosis or
treatment). Although there are some differences in the way in which source
contributors are categorised in Figures 1 and 2, it should be noted that
the average dose from natural sources dominates the dose from all other
sources combined, estimated to be 87% and 82% for the United Kingdom and
the United States, respectively.

Figure 1. Dose contribution to individuals in the United Kingdom

Figure 2. Dose contribution to individuals in the United States

III. What are the effects of ionising radiation?

The process of ionisation necessarily
changes atoms and molecules, at least temporarily, and thus may damages
cells. If cellular damage does occur and is not adequately repaired, it
may prevent the cell from surviving or reproducing, or it may result in
a viable, but modified, cell. The two outcomes have profoundly different
implications for the organism as a whole. Most organs and tissues of the
body are unaffected by the loss of even a substantial amount of cells,
but if the number lost is large enough, there will be observable harm
to the individual, reflecting a loss of organ or tissue function. The
likelihood of causing such harm will be zero at low doses but, above some
level or threshold dose, the damage will occur almost with certainty.
Above the threshold, the severity of the harm increases with increasing
dose. This type of outcome, which includes acute radiation syndrome, is
called deterministic, because the harm is almost bound to occur in exposed
individuals if the dose exceeds the threshold dose. The adverse effects
first observed in the early use of radiation were deterministic effects.
Threshold doses are substantially higher than the doses to workers and
members of the public expected from practices and sources in normal operation.
Only an accident involving a source capable of delivering high doses is
likely to cause deterministic effects.

The situation is very different if
the irradiated cell is modified rather than killed. Despite the existence
of highly effective defence mechanisms, the cloning of cells resulting
from the reproduction of a modified, but viable, cell may result, after
a prolonged and variable delay, called the latency period, in the manifestation
of a malignant condition (e.g., cancer). The probability of a cancer resulting
from radiation increases with increasing dose. This probability is assumed
for protection purposes to be without a threshold and to be proportional
to dose for doses below the thresholds for deterministic effects. Since
only the probability, but not the severity, of the cancer is affected
by the amount of dose, the outcome is called stochastic, meaning of a
random or aleatory nature.

If the radiation damage occurs in a
cell whose function is to transmit genetic information to later generations,
it is presumed that some harm, which may be of many different kinds and
severity, might be expressed in the progeny of the exposed person. This
type of stochastic outcome is known as hereditary. The probability of
hereditary harm also is taken to be proportional to the dose received.
In addition, irradiation in utero can lead to effects in children, principally
an increase in the stochastic risk of childhood leukaemia and a reduction
in IQ (intelligence quotient) following irradiation, mainly during the
eighth to fifteenth weeks of gestation.

Stochastic effects of radiation are
only detectable in epidemiology studies having sufficient statistical
power, and usually require large populations and years of follow-up to
cover the latency period of the exposed individuals studied. The estimated
risks of a radiation dose resulting in a stochastic outcome are derived
from a number of epidemiology studies, the most important being the study
of survivors of Hiroshima and Nagasaki atomic explosions. Radiation protection
standards based on stochastic risk estimates employ assumptions about
risk which are seen to be conservative in line with the degree of scientific
knowledge about the risk.

Based upon the wealth of scientific
knowledge to date and employing conservative assumptions, the likelihood
of stochastic outcome due to normal levels of radiation exposure is estimated
to be very small. For average exposure to natural background radiation,
the chance is of the order of 1 in 10,000 per year. For average exposures
in the population from many current practices, it is very much lower than
it is for background radiation.

IV. What are the protection principles upon which radiation protection
is founded?

As previously noted, the human activities,
such as those ranging from nuclear power production to radiation medicine,
that add radiation exposure to that which people normally receive due
to background radiation, or increase the likelihood of adding exposure
are termed practices. The human activities that seek to reduce the existing
radiation exposure, or the likelihood of incurring exposure which are
not part of controlled practices (e.g., radon in homes) are termed interventions.

For routine conditions involving practices,
most exposure of workers and members of the public is the result of normal
operating conditions. However, there may sometimes be variations in operating
conditions that cannot be regarded as normal. The term potential exposure
is used to describe exposure that is not certain to occur, (i.e., an exposure
caused by some departure from normality). Potential exposure reflects
the combination of the probability of occurrence of potential events,
the chance that such events will result in a radiation dose to individuals
and the probability of radiation effects from the expected resulting dose.

Bearing these distinctions in mind,
radiation protection for practices is founded on a conceptual framework
proposed by the International Commission on Radiation Protection (ICRP)
and involves three principles: justification, optimisation and limitation.

Justification . No practice involving
exposures to radiation should be adopted unless it produces sufficient
benefit to the exposed individuals or to society to offset the detriment
it causes. In the case of justification, detriment is not necessarily
confined to radiation, but may include other social and economic considerations
as well.

Optimisation . Once a practice has
been justified and adopted, it is necessary to consider how best to
use resources in reducing the radiation risk to individuals and the
population. For any particular source, the broad aim should be that
the magnitude of individual doses, the number of people exposed, and
the likelihood of incurring exposure which is not certain (potential
exposure) should all be kept as low as reasonably achievable, economic
and social factors being taken into account. Because of the interaction
of the various factors to be considered, methods for dealing with optimisation
are diverse. They range from simple common sense to complex techniques
such as cost-benefit analysis.

Limitation . Exposure of individuals
resulting from a combination of all relevant practices should be subject
to dose limits, or to some control of risk in the case of potential
exposure. These are aimed at ensuring that no individual is subject
to radiation risks deemed to be unacceptable. Limits provide a clearly
defined boundary of individual risk for application of the more subjective
procedures of justification and optimisation.

Intervention involves the application
of radiation protection principles retrospectively, i.e., when it is decided
to reduce existing exposure caused by an accident, contamination from
past practices or high natural background which is amenable to being reduced.
Two principles are involved in the case of intervention: justification
and optimisation.

Justification
. The proposed intervention should do more good than harm, i.e., the
reduction in radiation dose should be sufficient to justify the social
and economic costs involved. However, there will be some level of projected
dose for which intervention will almost always be justified because
of the acute radiation injury it will produce.

Optimisation
. The form, scale and duration of the intervention should be optimised
so that the benefits of the dose reduction less its costs are maximised.

Figure 3. Scope of radiation protection

The breadth of the conceptual framework for radiation protection has grown
constantly throughout the years, from the extremely simple guidance on
protection against X-rays issued in the 1930s up to the very comprehensive
system of protection which now covers practically all existing sources
of human exposure, artificial as well as natural, recommended by the ICRP
in its Publication 60. Figure 3 depicts this coverage.

V. How is radiation protection provided?

The conceptual
framework for radiation protection, as proposed by the ICRP, provides
a basis for operational criteria and guidance applicable to specific situations
(e.g., nuclear power, medical radiation therapy, chronic exposure to natural
radiation) developed by international intergovernmental organisations
such as the International Atomic Energy Agency (IAEA), the Commission
of the European Communities (CEC) and the Organisation for Economic Co-operation
and Development/Nuclear Energy Agency (OECD/NEA). Essentially, all countries
incorporate ICRP concepts in their radiation protection regulations and
practices.

Radiation
protection concepts, however, can only be implemented through an effective
infrastructure which includes adequate laws and regulations, an efficient
regulatory system, a well structured complex of experts and operational
provisions. It is also essential to establish an attitude and behaviour
shared by all those involved with protection responsibilities, from workers
through management levels, which ensures that protection and safety issues
receive the attention warranted as an overriding priority. This attitude
and behaviour is sometimes called a safety culture.

In general,
national legislation establishes a regulatory authority empowered to issue
regulations, authorise a registration and/or licensing of sources, conduct
inspections and take enforcement actions. While the regulatory authority
is empowered and responsible to the public for discharge of these functions,
registrants and licensees bear prime responsibility for the safety of
the sources in their possession. They are responsible for establishing
a safety culture within their organisation and are responsible for ensuring
safety of their workers and members of the public with regard to their
operations. Others, such as designers, manufacturers and constructors
have professional and legal responsibilities that are also significant
to safety.

A fundamental
component of radiation protection linked to the infrastructure is the
availability of adequate measurement equipment and techniques as well
as modelling and assessment methods and software. These are well developed
for most situations. It is also expected that the evolution of these protection
technologies will continue with gradual improvements in instrumentation,
modelling, assessment methods and quality control, in parallel with developments
in fields such as electronics, environmental studies and the nuclear industry
in general.

With respect
to the quality of radiation protection infrastructures, there is a significant
diversity of situations throughout the world. The OECD countries generally
have well established infrastructures for radiation protection, with exhaustive
and regularly updated regulations, strong and competent regulatory bodies,
adequate operational protection and emergency response structures, and
advanced research institutions as well as adequate measurement and assessment
technologies. There are obvious variations in the level and size of these
infrastructures, linked to the different levels of radiation and nuclear
power applications in the various countries, but, as a whole, the standard
of radiation protection across the OECD area appears good and sometimes
excellent. This conclusion is supported by trends showing significant
dose reduction in many practices through diligent application of the optimisation
of the protection principle in several OECD countries. The situation is
much more uneven in the rest of the world. Beside countries where the
infrastructure and the standard of protection are fully comparable with
those of the OECD countries, lie a large number of countries which do
not have a sufficient or even a significant infrastructure for radiation
protection. This is due to a lower degree of economic development or the
presence of significant political instability and, in several cases, to
a severe shortage of resources where priorities are assigned to more pressing
societal needs.

The new
International Standards for the Protection Against Radiation and the Safety
of Radiation Sources (BSS) developed through a joint effort by the Food
and Agricultural Organisation of the United Nations (FAO), the IAEA, the
International Labour Organisation (ILO), the OECD/NEA, the Pan American
Health Organisation (PAHO) and the World Health Organisation (WHO) provides
a set of conceptual and applicative recommendations appropriate for developing
protection regulations and operational requirements. The BSS will provide
valuable guidance in establishing or improving national radiation protection
infrastructures where they are not presently adequate.

VI. What are the significant issues and developments in radiation protection?

Radiation
protection is a dynamic field. The wealth of scientific knowledge upon
which it is founded increases constantly. There are new advances in technology
both with respect to providing protection and the use of radiation sources.
Also, regardless of the general status of protection, there are a number
of conceptual and practical issues which remain open.

There is
a growing feeling that future advances in biology might result in breakthroughs
in fundamental scientific knowledge which could change the dose-effect
relationship and risk models, and provide genetic analysis techniques
capable of identifying some specific radiation-induced tumours above the
general background of tumour incidence. Developments such as these could
affect how the principles for radiation protection are implemented. For
example, experimental data on adaptive responses or stimulation of cellular
repair at very low doses, if confirmed, could affect estimates of stochastic
risk of low doses and lead to revised approaches to situations such as
those involving intervention.

Some practices
are in a constant state of evolution with new technologies and procedures
replacing the old. The use of radiation in medicine is an example of such
a situation. Several models of power reactors based on new safety concepts
are being developed. Nuclear fusion is a truly new practice undergoing
long term development which may become a reality in the decades to come.
These are examples of the types of developments that can involve new radiation
protection issues and strategies. Also, another area which is expected
to reach an industrial dimension in the next few decades is decommissioning
of commercial nuclear power plants. Here, emphasis in radiation protection
should focus on optimised strategies for the protection of workers and
the public. Of particular interest is the practical application of the
protection principles to exempt wastes associated with huge amounts of
slightly contaminated scrap materials and valuable metals.

Applying
the concepts of protection against potential exposure to sources used
in medicine, industry and research as well as applying the concepts to
waste disposal, presents a particular challenge with much yet to be done.
Mistakes or accidents involving relatively simple sources have resulted
in serious injury and deaths. There is a need to improve the ability to
assess and manage the risks from potential exposure, particularly with
respect to accounting for the complete human-machine systems and interfaces
in safety evaluations. This is particularly important for radiation therapy,
because the margin of error is small when treating patients with high-radiation
doses. Since devices and procedures used in radiation medicine are constantly
evolving, keeping current with understanding and managing potential exposure
risk is particularly difficult.

Adequate
treatment of the long-time aspect (thousands of years) of waste disposal
is a difficult problem with respect to potential exposure. Although there
seems to be a consensus that the radiation protection objective of waste
disposal is not to subject people in the future to a risk that is significantly
greater than society is willing to accept now, the challenge consists
in demonstrating the case against specific national performance criteria
to the satisfaction of the regulatory authorities. It involves a very
complex safety analysis of the disposal system. The main difficulties
in providing a robust safety analysis for disposal are a lack of information
about the frequency of disruptive events, lack of feedback from operating
experience and design evaluation, and lack of environmental models for
the future. Overcoming these difficulties requires the concerted efforts
of radiation protection, waste management and other specialists at both
international and national levels.

Finally,
there is the social dimension of radiation protection. Radiation causes
public anxiety regardless of how well present radiation practices enable
persons to live in relative safety with radiation. The cause of this anxiety
is only speculative and probably cannot be attributed to a single cause,
but rather a combination of things, such as its association with nuclear
weapons, the fact that it cannot be detected by the human senses and that
it can produce cancer. This has led to a keener sensibility to the costs
than to the benefits of some radiation practices.

For this
and other good reasons, decision-making in several areas of radiation
protection cannot be isolated from its social dimension and must involve
the social parties affected. Better involvement of social parties in radiation
protection decisions requires improvement in the information provided
and education of interested parties about radiation, its benefits and
impacts, and the protection against these impacts. Although society is
showing an ever increasing interest and willingness in being involved
in decisions affecting life and well-being, from the standpoint of radiation
protection, a reinforced and better focused effort is needed.

VII. Conclusions

The present
conservative concepts and models for radiation protection provide adequate
protection. The standard of radiation protection across the OECD areas
appears good and sometimes excellent. A similar conclusion can be drawn
for some, but not all, countries throughout the world.

Radiation
protection is a dynamic field. It has undergone a significant evolutionary
period during the past few decades. General improvement of protection
techniques and technology is expected to continue. In addition, much is
going on in fundamental research, particularly in the molecular biology
area, which could alter the scientific foundation upon which today s protection
is based. This could lead to more efficient use of resources allocated
to protection, as well as other benefits.

There continues
to be a number of challenges for protection specialists. One, for example,
is satisfactorily addressing and demonstrating adequate protection for
those aspects of waste disposal, which continue to be the subject of public
controversy. Also, finding practical ways to apply the concept of potential
exposure to a variety of practices will require continuing development
effort. Another, and very important challenge, is involving the interested
social parties in protection decisions and adequately taking into account
the social dimensions of such decisions.

Because
of the dynamic nature of the protection field, the prospect of new radiation
and nuclear practices, and changing public attitudes toward risk, it is
important that the wealth of expertise and resources for protection and
related fields which has been accumulated so far is preserved in order
to guarantee adequate and cost effective protection.